The engine is a real Spitfire engine (according to him). But apart from that, he's building the plane up from scratch. Hes sourced all the plans and many other bits and pieces from aviation clubs in the UK and some other sources.
I once flew with him there (with easyjet... not with a Spitfire, lol) to go meet one guy who had some parts for his project.
I haven't spoken to him in a few years tho'... I wonder if he's completed a lot more of his project? He's also starting up a business trying to build a small and cheap helicopter ->
http://www.smartcopter.aero/